A venetian blind system is a popular window treatment that includes a plurality of horizontal slats designed to overlap when in a tilted closed position. Conventional venetian blinds suspend the horizontal slats as a group either from ladder drums or from a tilt-rail, via one or more ladder tapes or string ladders. The amount of light passing though the venetian blind system is regulated by raising, lowering and tilting the slats. The slats are raised and lowered by actuating a lift control such as a cord that either gathers or extends the ladder tapes by lifting a foot-rail. A tilt control such as, for example, a wand is used to rotate the ladder-drums or tilt-rail, which in turn causes the horizontal slats to rotate. Ladder drums are typically enclosed by a head-box secured to the top of the window opening. The tilt-rail is typically supported by a base-rail secured to the top of the window opening. In addition, the head box acts as a housing for other mechanical elements that facilitate the lifting and rotating of the slats and the base-rail acts as a mounting base for similar mechanical elements.
Conventional venetian blind systems are limited in the profile width of the slats. The slats of conventional venetian blinds are typically positioned within the window frame so that the window frame can provide privacy when the slats are in a tilted-closed position. Because the depths of many window frames are small and provide for a limited clearance distance between the slats and the window, wider profile slats must project out front of the window opening. As a result, when in the tilted-closed position, there is a lack of privacy at the sides of the window opening. Head-box systems also limit the profile width of the slats because of maximum mechanical tilt capacity. Wider tilt capacity results in higher cost.
In addition, the current design of conventional tilt rail systems increase the costs and complexity of wide span venetian blinds. In particular, conventional tilt-rails have relatively flat and elongated shapes that are susceptible to sagging. Such sagging can adversely affect the tilting function of the slats. To counter the undesired sag, conventional tilt-rails require additional supports that contribute to the costs and complexity of the venetian blind system.